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MECHANICAL 



353 
I R85J 



LIBRARY OF CONGRESS. 



Chaj). Copyright No..^:._._. 

fR^r 

UNITED STATES OF AMERICA. 



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A COURSE IN v* 



MECHANICAL DRAWING 



FOR EVENING SCHOOLS AND SELF-INSTRUCTION 



By LOUIS ROUILLION, B. S. 

Pratt Institute, Brooklyn, N. Y. 



1896 
THE PRANG EDUCATIONAL COMPANY 

BOSTON NEW YORK CHICAGO 







M^U'^fe-'^^^' 



Copyright, 1896, 
By The Prang Educational Company. 









S. J. PARKHILL& CO., BOSTON. U.S.A. 
PRINTERS 



PREFACE 



This course in Mechanical Drawing is the 
result of a number of years' work with even- 
ing classes, and has been evolved from a 
careful study of the needs of such classes. 
The course was originally issued in blue- 
print form, with accompanying typewritten 
notes. In this form it has been in use at 
the Pratt Institute and other schools, and in 
Y. M. C. A. classes, for the past four years. 
In a modified form it has appeared serially 
in "Machinery!'' The entire course has 
been carefully revised, and is now published 
in the more convenient form of a text-book. 

August I, 1896. 



The course covers a period of two school 
years of about twenty-four weeks each. 
Either two or three evenings a week may be 
devoted to the work. In the former case it 
may be found necessary to abridge the 
number of simple working drawings. The 
first twenty-four sheets constitute the work 
of the first year, and sheets XXV-XXIX 
that of the second year. 

The exercises given at the end of the book, 
form a parallel independent course permit- 
ting the use of the book as a text-book in 
class work. 

Louis Rouillion. 



CONTENTS 



PAGE 

General Instructions. 

Required Materials, i 

Use of Materials 2 

Drawing Board — Paper — T-Square — Triangles 
— Compasses — Drawing Pen — Pencils — 
Scroll — Scale — Ink. 

Lettering 7 

Models, 8 

REGULAR COURSE. 

Sheet I. Cubes, 12 

Sheet II. Triangular and Hexagonal Prisms, . 14 

Sheet III. Projection of a Square Pyramid, . 16 

Sheet IV. Projection of a Cross, .... 18 

Sheet V. Hollow Cylinders, 20 

Sheet VI. Moitise and Tenon Joint, ... 22 



PAUK 

Sheet VII. Door Joint 24 

Sheet VIII. Development of a Cube, . . 26 
Sheet IX. Development of a Square Pyramid, . 28 
Sheet X. Development of a Truncated Hexa- 
gonal Prism, 30 

Sheet XI. Development of a Cylinder, . . 32 

Sheet XH. Development of a Cone, ... 34 

Sheet XIII. Development of a Four-Piece Elbow, 36 

Screw Threads, 3^ 

Sheet XIV. Screw Threads, 4° 

Sheet XV. Springs, 42 

Sheet XVI. Bolts and Nuts 44 

Sheet XVII. Wrench, 46 

Sheet XVIII. Seven-inch Pulley, 48 

Sheet XLX. Cone Pulley, 5° 

Sheet XX. Flange Coupling, 52 



VI 



CONTENTS — Continued. 



PAGE 

Sheet XXI. Pillow Block, 54 

Sheet XXII. Clamp, 56 

Sheet XXIII. Monkey Wrench 58 

Sheet XXIV. Globe Valve, 60 

Notes on Working Drawings, 63 

I. Size of Sheets — 2. Title, Index, etc. — 
3. Sketches — 4. Laying-out Work — 5. Re- 
lation of Views — 6. Sectioning — 7. Inking 
— 8. Dimensioning — 9. Tracings — 10. Gen- 
eral Notes. 



PAGE 

Blue-Printing 67 

Sheet XXV. Assembly Drawing of a Bench Lathe 70 
Sheet XXVI. Details of Head-Stock, ' .v . 
Sheet XXVII. Details of Tool-Rest, . . . 
Sheet XXVIII. Details of Tail-Stock, . . . 
Sheet XXIX. Details of Bed, .... 



72 

74 
76 
78 



PARALLEL COURSE. 
Exercises I-XXIX, 



83 



COURSE IN MECHANICAL DRAWING. 



GENERAL INSTRUCTIONS. 



REQUIRED MATERIALS, 

In order that acceptable work may be 
•accomplished, fairly good instruments should 
be provided. The cheap brass sets that are 
sometimes offered by dealers for use in 
schools are worse than useless. The advice 



of some one experienced in draughting in- 
struments should be sought before pur- 
chasing. The following list of materials 
required for this course gives approximate 
prices that may be considered as inexpensive 
as it is advisable to obtain. 



LIST OF MATERIALS. 



Drawing board, about 16x23 inches 
Compasses, 5^ inches, with needle point, 

pen, pencil and lengthening bar 
Drawing pen, 4J inches 
T-square, 24-inch blade 
45° triangle, 9 inches . 
3o°-6o° triangle, 11 inches . 
Scroll 



$ .40 

2.00 

■5° 
.20 

•35 
•35 
•25 



Pencils : 

12-inch boxwood scale, flat, graduated 

to ^ inch the entire length 
Bottle of liquid India ink 
Tacks .,,.,,, 
Pencil and ink eraser , , , . 

Drawing paper. 



08 

40 

25 

05 
05 



88 



■■M 



COURSE IN MECHANICAL DRA WING. 



USE OF MATERIALS. 

Drawing Board. A light board having 
a smooth surface and the left-hand edge 
trued perfectly straight will serve as a draw- 
ing board. It should be somewhat larger 
than the largest sheet of paper that is to be 
used upon it. The left-hand edge serves as 
a guide for the head of the T-square. The 
left and right-hand edges should be com- 
posed of narrow strips, the grain of which 
runs across that of the board. 

Paper. The drawing paper should have a 
surface that will permit of considerable 
erasing without becoming roughened. When 
working by artificial light it is desirable that 
the paper be of a light-brown color which is 
less trying to the eyes than a pure white. 
Paper may be purchased in sheets 22x30 
inches, that make four exercise sheets, each 
measuring 11x15 inches. 

The sheet is tacked upon the board as 
shown in the Diagram opposite (Fig. i), 



being placed well over towards the left-hand 
side of the board, thus permitting greater 
firmness in the use of T-square and triangles. 

Thumb tacks may be used for securing 
the paper to the board, or one-ounce tacks, 
which should be driven well into the board. 
These latter have the advantage of offerins: 
less obstruction to the use of the T-square. 
When large sheets are used and the drawing 
requires considerable time, the paper may 
be stretched upon the board. 

The paper is stretched by turning up about 
an inch of the paper all around the edge and 
thoroughly wetting the trough thus formed. 
The edge is turned up to keep it dry, so that 
it may be used for glueing. See that the 
edge is firmly glued to the board. When 
the paper is dry it will be found to be 
smoothly stretched. When the drawing is 
completed, the sheet may be cut out with 
a sharp knife. The T-square or triangle 
should not be used as straight-edges for 
trimming sheets. 



GENERAL INSTRUCTIONS. 



DRAWING-BOARD, T-SQUARE AND TRIANGLES. 































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FIG. 1. 



COURSE IN MECHANICAL DRAWING. 



T-Square. The head of the T-square is 
always kept against the left-hand edge of the 
board and its upper edge is used in drawing 
all horizontal lines and for resting the tri- 
angles upon. 

Triangles. The triangles are used in 
drawing all straight lines other than horizon- 
tal ones. They are rested upon the upper 
edge of the T-square, and thus afford means 
of drawing vertical lines and lines at 30", 45° 
and 60°. By placing one triangle upon the 
other, angles of 15° and 75° may be obtained. 
A perpendicular may be drawn to any line 
situated at an angle other than those men- 
tioned, by placing either triangle upon the 
other so that its hypotenuse coincides with 
the line, and then revolving it through an 
angle of 90°. 

Compasses. The compasses are supplied 
with needle-points, pen and pencil, and are 
used for drawing circles and arcs of circles. 
By placing needle-points in each of the legs. 



the compasses may be used as dividers in 
stepping off distances. Supposing it is 
required to divide a given line into seven 
equal parts. The compasses are opened to 
an approximation to one of the parts and 
seven of these parts are stepped off lightly, 
without puncturing the paper. The error is 
noted and the compasses reset to a closer 
approximation, and the process continued 
until the required division is obtained. The 
paper is then lightly punctured at each step. 
The line may be either straight or curved. 
Determining a point by a needle prick has 
the advantage over a pencil-point in that it 
is not lost by erasure, and is more accurately 
determined. The position of the point is 
emphasized by drawing a small circle in 
pencil about it. 

For penciling circles or arcs of circles, the 
pencil is placed in one leg of the compasses 
and the needle-point in the other. The legs 
should be bent at the joints until the lower 
extremities are parallel, or nearly so. The 



GENERAL INSTRUCTIONS. 



compasses are held at the joint, rotated 
clockwise, and inclined slightly in the direc- 
tion of the line. A slight pressure is exerted. 
In inking, the pen is substituted for the 
pencil, and the weight of the compasses is 
sufficient to cause the ink to flow. 

Drawing Pen. The pen is filled by drop- 
ping the ink between the nibs while held in 
a nearly vertical position. 

In inking, the pen is held between the 
thumb and forefinger. Care should be taken 
that the nibs are not pressed together while 
the pen is thus held, as a line of varying 
thickness would result. 

The flat side of the point is laid against the 
edge of the T-square or triangle and the pen 
held within the plane of that edge. The 
taper to the point is sufficient to throw it far 
enough from the edge to prevent blotting. 
The handle should be tilted about 35° to 
the right of perpendicular. Draw from left to 
right and from the bottom to the top. The 



breadth of a line may be controlled by the 
adjusting screw. 

If the pen is not in use, even for a short 
time, the ink should be taken out, as it 
evaporates quickly and clogs the pen. For 
this purpose, pass the corner of a piece of 
chamois skin between the nibs of the pen. 
Keep the nibs of the pen at all times bright 
and clean. 

Pencils. A soft pencil, sharpened to a 
round point, should be provided for putting 
in letters, figures, arrow-heads and other 
free-hand work, and for making sketches. 
A hard pencil, sharpened to a flat chisel-like 
edge, should be used for drawing all lines 
with the aid of the instruments. The pencil 
should be used lightly, so as not to indent the 
paper. A small flat file, or a piece of fine 
sand-paper should be at hand, over which the 
pencil may be occasionally rubbed. For 
erasing pencil marks, a soft rubber should be 
provided, and a hard or sand rubber for 
erasing ink. 



COURSE IN MECHANICAL DRAWING. 



Scroll. The scroll is used in obtaining 
curves other than arcs of circles. If a curve is 
to be passed through a number of predeter- 
mined points, it should first be sketched in 
lightly free-hand. A section of the scroll is 
then applied to the curve so as to embrace 
as many points as possible. Only the cen- 
tral points of those thus embraced should be 
inked in. This process is continued until 
the desired curve is completed. 



of an inch upon the drawing. Take a slip of 
paper and measure off upon its edge five- 
eighths of a foot. Divide this distance into 
twelve equal parts, and each of these divis- 
ions into halves, quarters and eighths. In 
using such a scale treat it as though it were 
a full scale ; e. g., if the object being drawn 
measures 1 1^ inches, read ii^ inches from 
the reduced scale, make the drawing accord- 
ingly, and dimension as 1 1^ inches. 



Scale. When practicable, objects should 
be drawn full size. When an object is too 
large to permit of this, it may be drawn to 
the largest convenient scale. With the 
measuring scale recommended for this course 
drawings may be made to half or quarter scale. 
By half -scale is meant that each half-inch upon 
the drawing represents afull inch upon the ob- 
ject. A special scale may be made as follows : 
Supposing it is desired to make a drawing to 
five-eighths scale ; that is, that each inch upon 
the object will be represented by five-eighths 



Ink. The liquid India ink that comes in 
bottles is generally used for school work, and 
answers all requirements. Some draughts- 
men prefer the stick ink, which gives some- 
what better results, but requires preparation. 
Black ink alone should be used, except on 
tracings where lines that may be printed 
lightly, as dimension and construction lines, 
may be in red ink. Do not place too much 
ink between the nibs of the pen. A column 
of from one-quarter to three-eighths of an 
inch high is all that should be used at a time. 



GENERAL INSTRUCTIONS. 



LETTERING. 

It is desirable to confine the lettering of 
drawings to one or two standard alphabets 
that are plain and distinct, and the principles 
of which are easily acquired. These con- 
ditions are fulfilled in the Gothic fonts 
shown in Fig. 2. To analyze each letter 
and study its correct proportions and relations 
to other letters under varying combinations, 
would consume more time than can be alloted 
in this course. Therefore, a simple expedient 
may be resorted to, by which all the capitals, 
with the exception of I, J, M, and W, may be 
considered as having the same breadth. This 
breadth should be about five-sixths of the 
height. The inclination of the slant let- 
ters is about 20 degrees to the right of 
perpendicular. The upper parts of letters 
are made slightly smaller than the lower 
parts. The basis of the curved lower-case 
letters of the vertical font is a circle. 
Other characteristics may be noted by a 
careful inspection of the examples given. 



All lettering should be free-hand. Keep 
the pencil sharpened to a fine, round point. 
If the lettering is to be done in ink, a com- 
mon writing-pen may be employed, or the 
drawing pen may be used as an ordinary pen. 

The titles for the sheets given on the 
following pages are composed of tV-inch 
letters. The O of the lower-case has a 
diameter of \ inch. 

In putting the title upon a sheet, first draw 
two lines t\ inches apart along the edge of a 
slip of paper and sketch in the title, to 
ascertain the amount of room it will occupy. 
Then draw lightly upon the sheet, | inches 
below the top marginal line, two horizontal 
lines -^ inches apart, and the central vertical 
line of the sheet. Fold the slip of paper so 
that the end letters of the title will coincide. 

The fold will then be the centre point of 
the title. Lay the slip directly below the 
lines drawn on the sheet, so that the centre 
point of the sketched title will coincide with 
the centre line of the sheet. The location of 



8 



COURSE IN MECHANICAL DRAWING. 



the title is thus quickly determined and may 
now be carefully drawn, using the sketch as 
a guide. 

The dimension-figures should be a scant 
eighth-inch in height. The division line of 
fractions should be parallel to the direction 
of the dimension line. 

MODELS. 

Geometric models are chosen as the sub- 
jects for the earlier exercises, as they are so 
simple in form. Moreover as types of all 



forms, they present the underlying forms in 
mechanical construction, however complex 
that construction may be. They serve, then, 
not only as simple models for elementary 
practice, but also as giving the form basis 
for the most advanced work. The geometric 
models presented are — cube, equilateral trian- 
gular prism, hexagonal prism, square pyramid, 
cone, hollow cylinder, truncated hexagonal 
prism, and cross. It will be well for students 
to study the models and objects in making 
the drawings. 



LETTERING. 



ABCDEFGHIJKLMNOPQRSTUVWXYZ 

1234567890a 

abcdefqhijklmnopqrstuvwxyz 

ABCDEFCHIJKLMNOPQRS TUVWXYZ 

1234567690a 
abcdefghijklmnop qrstuvwxyz 



FIG. 2. 



REGULAR COURSE 



REGULAR COURSE EXERCISES. 



SHEET I. 



Cubes — Top and Front Views. 



This sheet gives the top and front views of a cube 
in three positions — facing, turned at 45°, turned 
at 60° and 30°. At the left of the sheet the top 
and front views of the cube facing are sliown. Draw 
a 2-inch square as shown in the upper left-hand corner, 
using the upper edge of the T-square for the top and 
bottom lines and a triangle resting upon the T-square 
for the sides. This is the top view of the cube 
facing. Continue the vertical lines below the lower 
horizontal line, the top view thus obtaining the 
side lines of the front view, and draw the top and 
bottom lines two inches apart. The two views 
required are now completed. After the drawing is 
finished the dimensions should be put on. As a cube 
has length, breadth and depth, three measurements 
should be given. The length and breadth are here 
shown on the front view and the depth on the top view. 

In the centre of the sheet two views of the cube 
turned at an angle of 45° are shown. The top view 



must first be drawn and is obtained with the 45° 
triangle. From the corners lines are dropped as in 
the first case and the top and bottom lines are drawn, 
completing the front view. 

At the right of the sheet, two views of the cube 
turned at 60° and 30° are shown. The top view is 
turned so as to form angles of 60° and 30° with the 
horizontal. The 60° and 30° triangle is used in 
drawing this view. The front view is obtained as in 
the previous cases. It will be seen that whereas in 
the second case the front and back edges of the cube 
coincide in the front view, in this case the back edge 
falls to the right of the front edge and is hidden. 
This is shown by putting in the back edge with a 
broken line, called a " hidden hne." The lines here 
used in showing the relation of the top and front 
views are called "construction hnes," made up of 
dashes a scant -^ inch in length. Directions for 
drawing hidden lines are given on page 66. 



SHEET I 





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COURSE IN MECHANICAL DRAWING. 



SHEET II. 



Triangular and Hexagonal Prisms. 



Prisms are solids having their ends parallel, and 
the edges formed by their sides parallel, and are 
known as triangular, hexagonal, etc., from the form 
of their bases. Before making the drawings, consider 
how to place them well upon the sheet. 

Two views of the equilateral triangular prism are 
given. First draw the equilateral triangle for the top 
view, using the 60° triangle for the sides, and com- 
plete the two views to the dimensions given. 

In the case of the hexagonal prism, three views are 
shown: the top, front and left-hand views. To obtain 
these, first draw a hexagon with li inch sides for the 



top view. This is done by drawing the lower line and 
cutting off the desired length. Then with the 60° 
triangle draw the lower side lines and cut off i| 
inches. The upper side lines are also drawn with 
the same triangle and the hexagon is completed by 
adding the top line. The front view is obtained 
as in the case of the triangular prism. The height 
in the side view is the same as in the front view, and 
distances from side to side are obtained directly from 
distances from top to bottom in the top view. This 
relation of the top and side views is shown in the 
drawing by the construction lines. 



SHEET II 



TRIANGULAR -^'^ HEXAGONAL PRISMQ 




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COURSE IN MECHANICAL DRAWING. 



SHEET III. 



Projection of Square Pyramid. 



1 his sheet shows the relation of the various views 
of an object and the proper method of projecting one 
view from another. 

First draw the base hne of the pyramid in the front 
view at an angle of 30 degrees to the horizontal and 
cut off the required length of two inches. At the 
centre of this base line erect a perpendicular to it to 
serve as a centre line. This is drawn with the 60- 
degree triangle. Mark off on this centre line a 
distance of four inches from the base line. Join this 
point with the extremities of the base line, complet- 
ing the front view. At a suitable distance, say two 
inches, above this view, draw a horizontal line as the 
centre line of the top view, and one inch on either 
side draw lines parallel to it. Complete the fore- 
shortened view of the base by drawing vertical lines 
upward from the extremities of the base line of the 
front view. The apex of the pyramid is on the centre 
line. The point is determined by drawing a vertical 
line from the apex in the front view, and is where tliis 
line intersects the centre line. Complete the top 
view by joining the apex to the corners of the base. 



To obtain the left-hand view, first draw the vertical 
centre line at a convenient distance to the left of the 
front view. This centre line corresponds with the 
centre line shown in the top view, therefore all dis- 
tances above the centre line in the top view are equal 
to distances to the left of the centre line in the left- 
hand view, and distances below the centre line in the 
top view are equal to distances to the right of the 
centre line in the left-hand view. As in Sheet II these 
relations are shown by construction "lines. For the 
base line, therefore, measure off one inch either side 
of the centre line, and erect perpendiculars for the 
sides of the base. Cut off the required length by 
projecting a horizontal line from the tilted-up corner 
of the base in the front view, and complete the view 
as in the case of the top view. The right-hand view 
is obtained in a similar manner. 

In inking, show all edges that are actually seen, by 
full, strong lines. Where an edge is hidden by a face 
in front of it, show it by " hidden lines." Centre 
lines are drawn lightly, and are made up of dashes 
alternately one-half and one-eighth inches long. 



SHEET III 



PROJECT/ON or SQUARE RYRAM/D 


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COURSE IN MECHANICAL DRAWING. 



SHEET IV. 



Projection of Cross. 



This sheet emphasizes the method of projecting 
one view from another, and shows how any one view 
may be obtained directly from two other views by 
this means, and also how a view is rotated so as to 
show three sides. 

Draw the top and front views of a cross to the 
dimensions given as shown at the left of the sheet. 

For the central group, tip the front view 30° to the 
right, and obtain the top view by projecting similar 
points from this view and the top view of the left- 
hand group. Care should be used in getting the 
hidden lines correctly. 

In the left-hand group the cross is shown standing 
erect on its base and squarely facing the observer. In 



the central group it is shown still facing the observer, 
but tilted to the right. In the right-hand group it is 
desired to show the cross turned 30° away from the 
observer, while still tilted as before. The turning of 
an object about a perpendicular axis may be shown 
by turning the top view in the desired direction and 
through the desired angle. 

Therefore, as we want to show the cross turned 
away at an angle of 30°, we rotate the top view 
through the required angle. The final view is obtained 
from this rotated top view and the front view of the 
central group. One face A B C D is shown pro- 
jected, 
various views 



Similar letters refer to similar angles in the 



SHEET IV 




20 



COURSE IN MECHANICAL DRAWING. 



SHEET V. 



Hollow Cylinders. 



This sheet introduces the use of the compasses. 
In one leg of the compasses insert the needle-point, 
and in the other leg insert the pencil, carefully 
sharpened. 

Locate the centre lines and draw the two con- 
centric circles to represent the top view of the cylinder 
at the left. Then draw the front view by projecting 
the side lines from the top view. 

The view shown immediately to the right of these 
two views is known as a " sectioned " view. Imag- 
ine the cylinder cut in halves from top to bottom. 
The back half would present the appearance shown 
in the sectioned view, the "cross-hatching" or 
"sectioning" representing the cut surface. The 
sectioning is done by drawing a series of parallel 
lines about -^^ inches apart. Lay the 45° triangle on 
the upper edge of the T-square and draw the topmost 
line of the sectioning. Then slide the triangle along 
the T-square for each successive line. As far as 
possible, draw both sides with one placing of the 



triangle. The sectioning should be inked in without 
previous pencihng and the lines should be finer than 
the lines of the cylinder. Various devices are in use 
for mechanically equalizing the distances in section- 
lining, but the trained eye is the most practical 
method. When two abutting pieces are sectioned, 
the section-lining on one piece slants in an opposite 
direction to that on the other. 

The right-hand drawing is that of a hollow cylinder 
with a flange about the top and bottom. In practice, 
when an object to be sectioned is the same on both 
sides of its centre line, only one side is sectioned 
while the other side is drawn in full. This method is 
here shown. In the front view, the part to the left 
is drawn in full and that to the right is drawn in 
section. The top view is drawn in full, as though 
the front view were not sectioned. 

Construction lines are omitted in inking, therefore, 
upon this and succeeding sheets the construction lines 
are not shown. 



SHEET V 




22 COURSE IN MECHANICAL DRAWING. 



SHEET VI. 

Mortise and Tenon Joint. 



An application of some of the foregoing principles cut in the centre of the end piece, into which a tenon, 

is here made in a simple working drawing of a cut upon the other piece, closely fits. This is clearly 

mortise and tenon joint. A mortise |x if inches is shown by the drawing. 



SHEET VI 




24 



COURSE IN MECHANICAL DRA WING. 



SHEET VII. 

Door Joint. 



A working drawing of a slightly more complicated 
joint is here shown. The front and side views are 
sufficient to make the joint from, but the top view is 
added to make the method of constructing the joint 
somewhat clearer. This joint is an end mortise and 
tenon joint and has a rabbet cut on the inside faces. 



The rabbet is shown by the section at the lower part 
of the drawing. The section illustrates a method 
commonly used for showing transverse construction. 
The material is supposed to be cut through at right 
angles to the face and the cut surface turned up until 
it lies in the plane of the face. 



SHEET VII 




26 



COURSE JN MECHANICAL DRAWING. 



SHEET VIII. 



Development of Cube. 



By the development of the surface of an object is 
meant the laying out of the pattern which, when 
properly folded, will exactly represent the surface of 
the object. 

A simple and easily conceived development is that 
of a cube. It is necessary to know the dimensions of 
the faces and the number of faces, six. For example, 
let each face be 2-|- inches square. Draw a square 
to these dimensions and let it represent the front 
face. Immediately above and below draw the top 
and bottom faces, and at the left and right the side 



faces, and adjoining either side, add the back face. 
Such a drawing is here shown. If cut out and folded 
along the lines connecting the squares, the result 
would be a 2^-inch cube. 

An aid to a clearer comprehension of the principles 
involved in laying out patterns, and also a check to 
the accurateness of the work, may be obtained by 
duplicating this and the succeeding five patterns upon 
a sheet of thin card-board or stiff paper and folding 
to the desired shape. A lap, for pasting, should be 
added along outer edges. 













SHEET VIII 




DEIVELOPMEINT °^ CUBE! 
































V 

C 


— 












-i 


1 















28 



COURSE IN MECHANICAL DRAWING. 



SHEET IX. 



Development of Square Pyramid. 



Draw the top and front views of a pyramid having 
a base 2 inches square and an altitude of 4 inches, 
and develop its surface. 

To obtain the development of the surface of the 
pyramid it will be necessary first to carefully study 
the two views. These show that the pyramid has 
four sides and a base, and that the sides are equal 
triangles successively joined together. All that is 
required, then, is to draw four equal triangles joined 
together about their vertices, and upon one of the 
triangles to join the square base. As two sides of the 
triangles are equal and meet in a point, they may be 
considered in the pattern as radii of an arc of a 
circle. The next step is to find the length of this 
radius. A top view of one of the sides of the face 
triangles is shown at A B, and a front view of the 
same line is shown at C D. But this front view of 
the line is foreshortened, and it is required to find its 



true length. Imagine the pyramid rotated about its 
axis so that the line A B would assume the position 
A E. Then the projection of this line in the front 
view is C F, which is the required true length. This 
exemplifies an important rule for developments, that 
the true length of each line must be ascertained, and 
also that the projection of the true length of a line 
will show as a horizontal line in a top view. 

Having now found the true length of a side, C F, 
this length is taken in the compasses and an arc of 
indefinite length is described. From some point ia 
this arc as a centre, and with a radius equal to a side 
of the base, an arc is drawn cutting the first arc. 
The two points are joined by a chord which repre- 
sents the base of one of the triangles. This base 
line is laid off four times and the various points joined 
to the centre of the arc. Upon one of the chords a 
2-inch square is drawn, completing the pattern. 



SHEET IX 



ll 




DEZVELOPMENT or SQUARE PYRAI\/1ID. 




\ 


k~^' 


^ 






Vl y^ 




— - rfT ^^^■'^^ \ 






/ 




/ ^ \ 




/ 


/ 




/ \ \ 




c 


\ .Pp--7 


/ \ 




\ /Cm/ 




1 




\\ f ^^M^ 






D r 



30 



COURSE IN MECHANICAL DRAWING. 



SHEET X. 



Development of Truncated Hexagonal Prism. 



Draw the top and front views of a hexagonal 
prism, each face of the hexagon being i-g- inches, and 
at 2I- inches from the base, measuring along the left- 
hand edge, pass a cutting plane making an angle of 
45° with the base. Also develop the entire surface 
of the truncated prism thus formed. 

As the sides of the hexagon are equal, their 
development is a line six times i-g- inches long. There- 
fore, draw a line 6f inches long as the base line of 
the pattern, and for convenience in projecting, let 
it be in the prolongation of the base line of the prism. 
Divide this line into six equal parts, and at the 
points of division erect perpendiculars. On these 
lines cut off distances equal to the cut edges of the 
prism. This may be done directly by projection from 
the front view. Connect the tops of hues, and attach 
a regular hexagon to one of the sides. In order to 
find the true shape of the top it will be necessary to 
make a view at right angles to it in the front view. 
At right angles to the cut face draw a line, and at 
some point in it draw another line at right angles to 



it. This latter line is shown at C D. From C and E 
in the front view project lines at right angles to the 
cut, through C and E, E in the oblique view. As 
the point C is on the centre line in the top view, it 
will also be on the centre line in the oblique view. 
On the line projected from E in the front view, the 
positions of E, E must be determined. As the line 
C D is only another position of the line C B, the 
distances of E, E from C D and C B must be the 
same in botli instances. The positions of these points 
being determined, together with that of C, the 
remaining points are obtained in a like manner and 
joined in their regular order. 

It now only remains to transfer this true shape of 
the cut surface to the rest of the pattern. Select any 
side as a connecting side. Then, as any point is 
determined by its distance from any two other 
points, each of the corners may be located by two 
intersecting arcs, the radii of which are equal to 
the distances from any two points previously found. 



SHEET \ 




32 



COURSE IN MECHANICAL DRAWING. 



SHEET XI. 



Development of Cylinder. 



Draw the top and front views of a cylinder to the 
dimensions given, and develop the side and top 
surfaces. 

As the circumference of a circle is 3. 141 6 times 
the diameter, the development of the side of the 
cylinder would be a rectangle 3.1416 times 2 inches 
long and 4 inches wide. The customary practice, 
however, is to divide the top view into a number of 
equal parts and step off with the dividers the same 
number of equal parts for the development. In the 
drawing, one-half of the top view is shown divided 
into twelve equal parts, therefore twenty-four of the 
parts are laid off along the base line of the pattern. 
The divisions of the top view are projected along the 
front view as elements of the cylinder, and these 
elements are reproduced on the pattern when it is 
desired to show the development of a cut. A sup- 
posed cut is here shown in the front view by a 



construction line, and its development is shown on 
the pattern. Imagine the elements of the cylinder 
numbered from left to right and the elements of the 
pattern correspondingly numbered. Then, with the 
T-square, project the intersection of the first element 
of the cylinder with the cut, across to the first 
element of the pattern. The intersection of the sec- 
ond element with the cut is next projected to the 
second element of the pattern, and so on till the 
centre element of the pattern is reached. As the cut 
is the same at the back of the cylinder as in front, 
the right-hand side of the developed curve will be 
identical with the part already found, only reversed. 
Draw the curve in free-hand with pencil, and ink with 
the aid of the scroll. 

The true shape of the face of the cut is an ellipse, 
and may be found by the method shown in the 
previous sheet, for finding an oblique view. 



Sheet xt 




34 



COURSE IN AIECFfANICAL DRAWING. 



SHEET XII. 



Development of Cone. 



Draw the top and front views of a cone having a 
2-inch base and an altitude of 4 inches, and develop 
its surface. 

As in the case of the cylinder, divide the circum- 
ference in the top view into a number of equal parts 
and project these divisions upon the base line of the 
front view. Connect these projected points with the 
apex of the cone. To the right of the cone describe 
an arc, having a side of the cone as radius and the 
apex as centre. On this arc lay off the development 
of the circumference in the top view by stepping off 
the same number of equal parts as there are divisions 
of the circumference. Connect each of the points 
stepped off with the apex. By drawing a circle equal 
to that of the top view, tangent to the arc, the pattern 
of the cone is completed. 



If it is required to obtain the development of the 
frustum of a cone, the cut may be developed in the 
manner shown in the drawing. From the points of 
intersection of the cut with the various elements of 
the cone draw lines parallel to the base, cutting a side 



line. 



The true lengths of the cut elements are thus 



obtained. With the apex as centre, and with radii 
equal to the distances to each of the points found on 
the side line of the cone, describe arcs cutting the 
elements of the developed cone. The process is 
identical with that used in developing the cut of the 
cylinder, excepting that the points are projected by 
concentric arcs in the case of the cone and by parallel 
lines in the case of the cylinder. As in the previous 
sheet, the true shape of the cut face is an ellipse, and 
may be found by the method there indicated. 



D^VEILOPMIZNT- or CON EI. 



SIIKKT XI 




36 



COURSE IN MECHANICAL DRAWING. 



SHEET XIII. 



Development of Four-Piece Elbow. 



Draw the top and front views of a four-piece elbow, 
together with its development. 

The ellipses in the top view are obtained by pro- 
jecting the points of intersection of the joints in the 
front view with the elements, to corresponding 
elements in the top view. Five such points are 
shown at G, H,G, P and J. The top view is not required 
in obtaining the development, and is given only as an 
additional exercise in drawing. First draw a 2-inch 
cylinder of indefinite height. At i^ inches above the 
base draw a horizontal line D C, extending it to the 
left, one inch beyond the cylinder, and erect the 
perpendicular, C F. With the 3o°-6o° triangle 
divide the right angle thus formed into three equal 
angles. The sides of these angles serve as centre 
lines for the various parts of the elbow, and their 
bisectors, H J, K L, M N, are the joints. The angles 
may be bisected by stepping off two equal divisions 
on the quadrant serving as the centre line of the 
elbow. The joint M N, crossing the cylinder as first 



drawn, completes the lowest part of the elbow. To 
obtain the second part, draw lines from the extrem- 
ities of M N, at right angles to E C, until cut by the 
second joint K L. The remaining parts arfe obtained 
by the same method. 

The development of the lowest part is obtained as 
shown in Sheet XI. The two central parts are alike, 
therefore one pattern will sufiice. Draw a horizontal 
line E C, corresponding to the centre "line E C, in the 
front view. Cut off distances above and below the 
centre line of the pattern equal to the distances above 
and below E C in the front view : e. g., L N and K M. 
Connect the points found by a smooth curve. The 
upper part is obtained by stepping off the distances 
from corresponding elements of the upper part in the 
front view. Similar letters refer to similar points in 
each of the views. 

The distance that the point C is from the elbow 
determines the curvature of the elbow; the nearer 
the point, the sharper the turn. 



SHEET XIII 



DEI\/EZL-OPMENT or rOUR-PfEICEI EILBOW. 




r_ 


1 
1 
1 


" i 
1 


1 
1 


1 


\ 1 ~7 

1 _J ^! 


1 1 
1 1 
1 1 













^ — ^ 


"p' 












^ 


u---^ 












h 


r 








K 








38 



COURSE IN MECHANICAL DRAWING. 



SCREW THREADS. 



In the figure opposite, let A B C D represent a 
cylinder, and let the base line, D D, of the triangle be 
equal to the circumference of the cylinder. Imagine 
the side B D of the triangle placed against the 
element B D of the cylinder, and the triangle wrapped 
around the cylinder. The hypotenuse of the triangle 
would then present the appearance shown by the 
curve. Such a curve is called a helix, and the per- 
pendicular distance between the ends of the curve is 
known as its pitch. 

Another way of imagining a helix to be traced is by 
a point rotating about a centre and at the same time 
advancing in a straight line. This is clearly shown 
on a screw-cutting lathe in which the metal to be cut 
revolves with a uniform velocity and the tool is fed 
along a straight line parallel to the axis of the 
screw. 

It is customary to speak of pitch as the number of 
threads per inch rather than by the true pitch measure- 
ment. A thread of one-eighth-inch pitch is known as 
"8-pitch"; that is, there are eight threads to the 
inch. 



The following table is one that draughtsmen should 
be familiar with : 

sellers' or u. s. standard screw threads. 



Diam. 


Pitch. 


Diam. 


Pitch. 


Diam. 


Pitch. 


Diam. 


Pitch. 


\ 


20 


1 3 

16 


10 


u 


6 


^\ 


4 


T^6 


l8 


1 


9 


1 1 


Si 


2| 


4 


■ 1 


i6 


15 
16 


9 


If 


5 


m 


3h 


tV 


14 


I 


8 


li 


5 


3 


3h 


\ 


13 


iiV 


7 


HI 


5- 


3i 


3* 


9 
16 


12 


li 


7 


2 


4i 


3A 


3i 


f 


11 


u 


7 


2i 


4i 


3i 


3i 


H 


II 


lA 


6 


2t\ 


4i 


3t 


3 


1 


ID 


•1 


6 


2| 


4 


4 


3 



The standard thread in the United States is known 
as the Sellers' thread. The angle of this thread is 
6o degrees. One-eighth of the top of the thread is 
taken off and an equal amount added to the bottom, 
thus doing away with the sharp corners. A section 
of the Sellers' thread is shown in Sheet XIV, and 
also a section of a square thread. 



REGULAR COURSE EXERCISES. 



39 



Screw Threads. 



HELIX AND PITCH. 




FIG. 3. 



40 



COURSE IN MECHANICAL DRAWING. 



SHEET XIV. 

Screw Threads. 



At the upper left-hand corner of the sheet is shown 
the method of obtaining the curve of a screw thread. 
Divide one-half the circle into any number of equal 
parts and divide one-lialf the pitcli A H into the 
same number of equal parts, say six. Then project 
the points of division of the circle successively to the 
lines of division of the pitch, as A to A, B to B, C to 
C, etc. Connect the last series of points by a smooth 
curve. The root curve is obtained in a similar man- 
ner from the points of division on the inner circle. 
Observe that in a single-threaded screw the point on 
one side is directly opposite the root on the other. 

To draw the square-threaded screw, shown in the 
centre drawing, lay off the pitch along the sides and 
sketch in lightly the squares representing the deptli 
and width. The curves are obtained as in the case 
of the V-thread. Notice that part of the curves are 
hidden, and draw only such parts as appear in the 
front view. 



The method of representing screw threads just ex- 
plained is not used in working drawings, because of 
the amount of time and trouble it necessitates, and 
because the object of the drawing can be attained as 
well by a much simpler method. 

Various kinds of conventionalized threads for small 
screws are shown at the lower part of the sheet. 
That shown at the left is a common method. "The 
longer lines represent the tops of the threads and are 
drawn about one-eighth of an inch apart, regardless 
of what the pitch may be. The shorter lines are 
drawn slightly heavier and not quite to the sides of 
the thread. 

At the top of the sheet straight lines are sub- 
stituted for the curves of the V-thread, and at 
the right the thread is given a more finished 
appearance. In the centre of the sheet are shown 
two methods for drawing conventional square 
threads. 



SHEET XIV 




42 



COURSE IN MECHANICAL DRA WING. 



SHEET XV. 



Springs. 



This sheet shows conventional methods of repre- 
senting springs. The spring at tlie left may be con- 
sidered as a square-threaded screw from which the 
body has been removed. The curves, except at the 
ends, are shown as straight lines. 



The two springs at the right are of round wire, 
sections of which are shown. Draw circular arcs 
with centres an inch apart for the larger spring and 
three-eighths of an inch for the smaller one. Draw 
lines tangent to these arcs. 



SHEET XV 




44 



COURSE IN MECHANICAL DRAWING. 



SHEET XVF. 

Standard Bolts and Nuts. 



This sheet is designed to show the proportions of 
standard bolts and nuts. The diameter of the boU is 
the unit from which the various proportions are de- 
rived. In the drawing, the diameter of each of tlie 
bolts is taken as one inch. The lengths of the bolts 
are shown as indefinite. Complete the drawing to 
the standard proportions for finished bolts and nuts 
given in the Table, page 38. 

To draw the chamfer on the hexagonal nut or 
head, take a radius equal to the thickness of the 
nut and with centre at the intersection of the centre 
line and bottom of nut, describe an arc. The inter- 
sections of the arc with the sides of the front face 
determine the extremities of the two side arcs. By 
trial, find a point on the centre line of the side face 



for an arc passing through the top of the nut and the 
two extremities before determhied. The point is 
about one-quarter way down the centre line. The 
chamfer on the square nut is here shown as equal 
to that on the hexagonal nut. 

A hexagonal nut may be drawn with close approx- 
imation to accuracy by the following method, which 
dispenses with the drawing of the hexagon : First 
draw the centre line of the nut, and then the top and 
bottom lines equal to the diameter of the bolt. Draw 
the front face slightly narrower than this diameter, 
and take the width of each of the side faces as equal 
to one-half the front face. Add the chamfer, as 
above. Three faces of a hexagonal nut should be 
shown, and but one face of a square nut. 



SHEET XVI 




STANDARD BOLTS --° MUTS. 







ROUGH 


r/l\JISHED 


r 


/iD+i- 


J^D * 7^ 


T 


D 


D-7^ 



D= OuhJde diom of bolt 



F~= iShort d/om o/ head or nut 



T= Thickness of he-od ornut 



L. = Length of bolt 



P- Pitch. 



-p = No. threads per /nch 



46 



COURSE IN MECHANICAL DRAWING. 



SHEET XVII. 



Spanner Wrench. — ; Drop Forged. 



It is desirable tliat objects somewhat similar to 
those shown in this sheet and the sheets immediately 
following, be used as models. Where this is imprac- 
ticable, the drawings may be used as sketches. When 
a drawing is to be made from the object, a pencil 
sketch is first made. All sketches should be free-hand 
and carefully executed. The dimensions are taken 
from the object with foot-rule and calipers. 

Care should be exercised in the placing of dimen- 
sions. No general rule can be laid down, as the 
proper dimensioning of a drawing is a matter of 
experience. The draughtsman should be familiar 



with machine-shop practice, and put such dimensions 
on his drawings as best serves the purpose of the 
workman. 

This sheet shows a working drawing of a spanner- 
wrench, drop forged. All the curves are arcs of cir- 
cles, the centres of which it will be necessary to locate. 
Draw to the dimensions given. In making working 
drawings, first locate the centre lines and build 
the drawings up about them. The figures used in 
dimensioning should be about one-eighth inch in 
height, and be strong and distinct. In inking, put in 
all curves first and then the straight lines. 



SHEET XVir 




48 



COURSE IN MECHANICAL DRAWING. 



SHEET XVIII. 



Seven-inch Pulley. 



In 5heet V we learned that " when an object to be 
sectioned is the same on both sides of its centre line, 
only one side is sectioned, while the other side is 
drawn in full." In this sheet is found an application 
of this rule. The pulley is symmetrical about the 
centre of the shaft, therefore, in sectioning, one-half 
alone is shown. The lower half of the pulley is in 
outline, though the drawing would be quite as service- 
able without the hidden lines. 

As many dimensions as possible should be given on 
one view. The same dimension should not be re- 



peated. Where a dimension is given on a sectioned 
surface, the section-lining should not cross the figures. 
Do not crowd the figures. Where there is not room 
for both the figures and the arrow-heads between the 
lines to be dimensioned, the arrow-heads may be 
placed outside the lines, as shown at the upper right- 
hand corner of the sheet. See that all unfinished 



corners of castings are rounded. 



Draw to the given 



dimensions. To show the structure of a part, a cross- 
section is sometimes placed on the part, as shown on 
one of the spokes. 



SHEET XVIII 




5^ 



COURSE IN hlECHANiCAL DRAWING. 



SHEET XIX. 



Cone Pulley. 



When an end view of an object shows only circles, 
it should be omitted. Therefore, but one view of the 
cone pulley is necessary. The fact that an end vie\v 
would show as a series of concentric circles may be 
expressed by placing the abbreviation "d,"or "dia." 
after the dimensions that show diameters. 



Shafts should not be sectioned. Spindles, studs, 
nuts, bolts and screws are also included in this rule. 
An application of the rule is given in the drawing 
where the shaft is shown in full, while the pulley is 
shown in section. 



SHEET XIX 




52 



COURSE IN MECHANrCAL DRAWING. 



SHEET XX. 

Flange Coupling. 

The rule to which attention was called in the last is not sectioned, but also the bolt and nut. When 

sheet, that shafts should not be sectioned, is further two adjacent pieces are sectioned, the section-lining 

emphasized in this sheet, wherein not only the shaft takes a different direction in each. 



SHEET XX 



rLANQE COUPLING 




, Hey .f ^g. 



■f- 



«VJ I 



i " 






I 



54 



COURSE IN MECHANICAL DRAWING. 



SHEET XXI. 



Pillow-Block. 



As a full-size drawing of the pillow-block to the 
dimensions given would be too large for the sheet, it 
becomes necessary to draw it to a reduced scale. 
The scale should be as large as possible ; in this case, 
three-quarters of an inch to the inch. That is, for 
each inch measured upon the pillow-block, three- 
quarters of an inch is drawn. The dimensions should 
in all cases be the full dimensions of the object. 
Place a note upon the drawing, stating the scale to 



which it is drawn when other than full scale. Centre- 
line all holes and give the distance between centres. 
An endeavor has been made to adopt a standard 
section-lining to represent different- materials. A 
section-lining to represent Babbitt-metal is here shown. 
It consists of lines drawn at 30° or 60° in both direc- 
tions. The purpose of such section-lining is generally 
more easily and satisfactorily obtained by giving the 
name of the material in a note upon the drawing. 



SHEET XXI 



o 

o 



1^ 







56 COURSE IN MECHANICAL DRAWING. 



SHEET XXII. 

Five-inch Clamp. 

In long screw-threading, considerable time may be of the clamp. The necessity for an end view is 

saved by drawing the threads at the beginning and obviated by showing in section such construction of 

ending only. This practice is shown on the drawing parts as would be shown in the end view. 



SHEET XXII 




58 



COURSE IN MECHANICAL DRAWING. 



SHEET XXIII. 



Monkey Wrench. 



The pitch of the thread is here given in a note on 
the drawing as "Pitch-n"; it might be abbreviated 
to read "P-ii." If the thread is a left-handed one, 
it is so noted on the drawing, otherwise it is under- 
stood to be right-handed. A single-thread is under- 
stood unless otherwise noted. 

A scheme for putting in small dimensions is shown 



in the case of the topmost dimension on the sheet. 
Two arrow-heads embrace the part to be dimensioned 
and the shaft of one of the arrows serves as the 
division-line of the fraction. The interior construc- 
tion of the handle is here suggested, but not dimen- 
sioned. The cross-hatching indicates the knurling of 
the head of the bolt. 



SHEET XXIII 



MONKEY WREINCH. 




5o COURSE IN MECHANICAL DRAWING. 



SHEET XXIV. 

Globe Valve. 

The valve is symmetrical about its centre-line, ex- tlie valve seat is to break away a piece of the wall 

cepting the construction of the valve seat. One-half and show the entire valve seat in section. To avoid 

is in section and the left-hand side of the valve is crowding, some of the minor dimensions are omitted 

shown by hidden lines. Another method of showing in the drawing. 



SHEET XXIV 



<0 
Hi 

Q 



y-' 



""(f 



"^T — 

__l 



-^ . 



i^ 



globe: valvc 



^'± 




v^_ 



NOTES ON WORKING DRAWINGS. 






GENERAL DIRECTIONS. 

Practice in the various draughting rooms 
may differ in details, yet is uniform in princi 
pies. These principles we have been study- 
ing in the previous sheets of this course, and 
are about to apply them in making a complete 
set of working drawings of a bench lathe. 
For the sake of compactness, and the arrang- 
ing of a series best adapted for students' use, 
the set is made up of five sheets, the first of 
which is an assembly drawing, that is, a draw 
ing showing the assembling of all the parts 
into the complete machine, and the remain- 
ing four being each a detail sheet of the four 
parts of the lathe, head-stock, tool-rest, tail- 
stock, and bed. 

Other arrangements of sheets might advan- 
tageously be made ; c. g., all work for the 
forge-shop might be grouped together, and 



also all work for the iDattern-maker. In fact, 
it is the custom in some draughting rooms to 
make separate drawings for the machinist, 
the pattern-maker, and the blacksmith. Or 
all work required to be done on a certain 
machine, as a screw-cutting lathe, may be 
brought together. 

For convenience in reference, tne various 
points to which attention has been called 
in the sheets immediately preceding are 
here brought together under appropriate 
headings, and such notes are added as may 
be required for a comprehensive knowledge 
of prevailing draughting-room practice. 

I. Size of Sheets. Some system of 
uniform sizes of sheets is generally adopted 
in draughting-ofifices to facilitate handling 
and filing. A convenient system permits of 



64 



COURSE IN MECHANICAL DRA WING. 



a smaller sheet being made by halving the 
next larger. Such a scheme has been fol- 
lowed in this series. The paper comes in 
sheets, 22 x 30. Each sheet is cut into two 
sheets of 15x22, for large drawings, and 
again divided into sheets of 15x11 for the 
smaller drawings. The lathe drawings are 
made upon the larger sheets. The border- 
lines inclose a "sight" of 19^x13. Trim 
to f of an inch at the top, bottom and right- 
hand sides. A wider margin at the left 
permits of binding together the series of 
drawings. 

2. Title, Index, Etc. Leave a space of 
4x2 in the lower right-hand corner for title, 
etc. A method for titles is shown on the 
sheets. It consists of five parts : 

a — Name of Machine. 

(5— Detail. 

c — Scale. 

d — Date and Draughtsman. 

e — Index of Drawing. 



The letter of the Index should, if possible, 
bear some relation to the machine designated, 
e. g., L-Lathe. The first number is used to 
distinguish between various types of similar 
machines. The final number is the particular 
mark of the machine bearing it. In a com- 
plete set of drawings the assembly drawing 
should be indexed as number one, and should 
contain a list of the other drawings with 
their numbers. 

The heights of the letters in " a " and " d " 
are -^^ inches for capitals and | inch for lower- 
case letters. Other letters arid figures are 
I inch in height, excepting the index. Index 
letters and figures, ^.^., L-2-1 are | inches 
high. 

The firm's name should appear somewhere 
on each drawing. A common usage is to put 
this on with a stamp which sometimes in- 
cludes the date. 

3. Sketches. Sketches should be made 
with care and be of such a nature that a 



NOTES ON WORKING DRAWINGS. 



65 



correct drawing or even the thing itself could 
be made from them by another, if necessity 
demanded it. A pad of manila paper, about 
8x12, will be found handy for making 
sketches. The work should be free-hand. 

4. Laying out Work. Large sheets 
requiring considerable time may be stretched ; 
otherwise use tacks. 

Select such views as will best show the 
object and as few as will show it clearly. 

Find approximately the space each view 
will occupy and locate centre-lines. 

Build up each part about its centre-lines, 
not completing each view separately, but 
projecting lines from one view to 
another. 



view should be omitted, and the letter "d," 
or " dia." be used in dimensioning. 

6. Sectioning. When it is desirable 
to show in detail the internal structure, 
sectioning should be used. 

When an object is symmetrical about its 
axis, section but one-half. 

Do not section bolts, nuts, screws, studs, 
spindles, and shafts. 

The part of an object back of a sectioned 
view need not be shown. 

Two adjacent cut surfaces should be 
sectioned-lined in opposite directions. 

More than two cut surfaces may be dis- 
tinguished by varying the width of the 
section-lining, or its slant. 



5. Relation of Views. Where more 
than one view is required, place the top 
view above the front view, the right view 
to the right, and the left view to the left. 
When an end view shows only circles, this 



7. Inking. If original drawings are to 
be inked, use black ink only. It is sufficient, 
however, to have the original drawing in 
pencil, as a tracing can be made directly 
from it. 



66 



COURSE IN MECHAXICAL DRAWtXG. 



Show centre-lines by light dashes, alter- 
nately \ and \ inches in length. 

Show invisible parts by hidden lines made 
up of dashes about fV inches long. 

Construction lines should not be inked. 

Ink all curved lines first ; then the straight 
lines. 

When lines radiate from a point, stop them 
before reaching the point, to avoid blotting. 

Keep the pens sharpened. 

8. Dimensioning. Put in dimensions 
after the drawing proper is completed. 

All dimension figures to be, at least, a scant 
eighth-inch, and made to read, in horizontal 
dimensions from the bottom of the sheet, and 
in vertical dimensions from the right of the 
sheet. 

The division line of fractions should have 
the same direction as dimension lines. 

See that the arrow-heads rest against the 
lines dimensioned. 

Do not use centre-lines for dimension lines. 



Give dimensions in inches and fractions of 
an inch up to 24 inches. Above 24 inches 
use feet and inches, always indicating feet 
and inches, separated by a hyphen, thus: 
5'- o", which reads five feet, no inches. 

When the dimensions are in even feet, the 
inches should always be expressed by o ". 

Give each dimension once only, regardless 
of the number of views. 

Give dimensions over-all, that is, give the 
dimension of the whole in addition to the 
dimension of the parts. 

As far as possible confine dimensions to 
the one view. 

Designate a radius by"r" or"rad." and 
indicate the centre by a small circle. 

The full dimensions should be given re- 
gardless of the scale of the drawing. 

Dimensions should be placed upon the 
object, but where this would lead to crowding, 
the dimension may be placed adjacent to the 
object and connected by dashes- 
Give distances between centres of bolt holes. 



NOTES ON WORKING DRAWINGS. 



67 



9. Tracings. Centre and dimension lines 
on tracings may be represented by full red- 
ink lines. The arrow-heads should be 
black. 

Washes or crayon used for sectioning 
should be placed on the reverse side of the 
cloth. 

If the ink does not readily adhere to the 
cloth, the surface may be brushed with clialk 
or talc. 

10. General Notes. Use explanatory 
notes freely. 

"Finish " may be indicated by an "f," the 
cross-bar of the f being on the line to be 
finished. Or "finish" maybe indicated by 
drawing a line in red ink adjacent to the 
surface to be finished. 

The name of each piece and the number 
required for each complete machine should 
be marked directly over the piece. 

In long screw-threading show only the 
beginning and ending of the thread. 



A long object having the same construct- 
ion throughout a considerable distance may 
be drawn with its central part broken out. 

Do not use the scale as a ruler. 



BLUE=PRINTINQ, 

It is in the form of blue-prints that the 
drawings generally reach the shops. The 
prints are made by exposing chemically pre- 
pared paper to the action of the sunlight, 
and then washing in water. 

Prepared paper may be purchased from 
dealers in draughtsmen's supplies, or it may 
be easily made as wanted. The chemicals 
required for sensitizing the paper are Citrate 
of Iron and Ammonia, and Red Prussiate of 
Potash. These may be purchased at any 
drug-store and should not cost more than 
ten cents an ounce. 

For making enough blue-print paper for the 
set of drawings of the lathe, dissolve about one 
ounce of Citrate of Iron and Ammonia in 



6^ 



COURSE IN MECHANICAL DRAVVLXG. 



four ounces of water, and about three-quarter 
ounces of Red Prussiate of Potash in four 
ounces of water. The Prussiate of Potash 
will dissolve more readily if it is first pounded 
into a powder. The relative amounts of the 
chemicals used vary in practice, equal quan- 
tities of each being sometimes used. The 
quantities given above have been found by 
experience to yield a deep blue color. After 
the chemicals are dissolved they are mixed 
together, and the mixture is spread upon the 
surface of a good, white paper. A soft 
paste-brush, about four inches wide, will be 
found serviceable for this purpose. Apply 
the solution evenly over the entire surface, 
and tack the sheet up in a dark place to dry. 
The paper is now sensitive to the action of 
light, from which it should be carefully 
guarded. The drying requires about an 
hour. The paper may be kept for some 
time without deterioration. 

In offices where blue-printing is done, 
special printing frames are provided. These 



consist of a board upon which two or three 
thicknesses of flannel or other soft cloth is 
smoothly fastened, over which is hinged a 
sheet of heavy glass. The cloth furnishes a 
smooth, yielding surface upon which to place 
the paper and tracings, and the heavy glass 
presses them evenly together while permit- 
ting the sunlight to act. The prepared paper 
is placed upon the cloth, sensitized face up, 
and the tracing is placed over it. They are 
held firmly together by the glass, and ex- 
posed to the direct action of the sun's rays. 
The time of exposure varies with the in- 
tensity of the sunlight, but from ten to three 
o'clock an exposure of from five to eight 
minutes should be sufficient. The printing 
may be done without the direct action of the 
sun's rays, as upon a cloudy day, by extend- 
ing the time of exposure to from one to two 
hours. 

When the paper has been exposed long 
enough, which is shown by the yellow color 
changing to a bluish-gray, it is placed on a 



NOTES ON WORKING DRAWINGS. 



69 



bath of clean water, and allowed to soak If, after a blue-print is made, it is desired to 

for a few minutes. It is then rinsed off and add anything to it, as a measurement or a 

hung up to dry. line, it may be done with an ordinary pen 

If a regular printing frame is not attain- dipped in caustic soda, which bleaches the 

able, any simple device maybe used that will blue, or Chinese White may be used. 

keep the paper and tracing firmly pressed The finished parts of a machine may be 

together and not obstruct the action of the shown upon a blue-print by drawing lines 

sunlight. with red ink adjacent to such parts. 



70 



COURSE IN MECHANICAL DRAWING. 



SHEET XXV. 



Bench Lathe — Assembly Drawing. 



The assembly drawing, although numbered one, is 
the last to be drawn in the series. It is made directly 
from the detail sketches. The numbers upon the 
assembly drawing refer to the numbers of the various 
parts and show how they are assembled. 

For example, the head-stock frame in the assembly 
drawing is marked "2-1;" By looking at the "List 
of Drawings " given in the lower left-hand corner of 
the sheet, it will be seen that " 2 " is the number of 
the sheet containing the details of the head-stock, 
and that the number of the frame is " i " on that 
sheet. Again, the hand-wheel on the tail-stock is 
numbered "4-6," which means, detail number 6 on 
sheet number 4. 



As a rule, it is better not to shade a drawing. 
There are places where shade-lining tends to bring 
out more clearly the meaning of a drawing, but such 
cases are the exception. This sheet would be quite 
as serviceable without the shade lines. It adds some- 
what of a finish to the drawing, but is here given 
simply as an example, and to explain the method. 
The light is supposed to come from the upper left- 
hand corner of the sheet at an angle of 45°. There- 
fore, the bottom and right-hand lines are made 
heavier. The thickness of the shade line should be 
upon the outside of the line. 

Sometimes the principal over-all dimensions are 
shown on the assembly drawing. 



SHEET XXV 




/ - Aaaembly 
£-Head Stoch 
J- Too/ Heat 
•rf- 7ai/ ■Stocli. 
■S- Bed 



Bench Uothe 
Assembly. 



a-a-se. 



L-2-1 



72 



COURSE IN MECHANICAL DRA WING. 



SHEET XXVI. 



Bench Lathe — Details of Head- Stock. 



The designing of a machine and the making of the 
original drawings for it is not a subject to concern the 
student of elementary mechanical drawing. Tliat is tlie 
worlc of the experienced designer and draughtsman. 
The best practice for the student is to make drawings 
of some machine already built. 

Suppose the bench lathe under consideration to be 
such a machine. The first thing to do is to take the 
machine apart and make careful free-hand sketches of 
each part, fully dimensioning. Section-paper, a paper 
lightly lined to inches and fractions of an inch, will be 



found of assistance in making correctly proportioned 
sketches. From these sketches the mechanical draw- 
ing is made in pencil. As every one cannot have a 
machine to take apart and make sketches of, the 
student may consider these sheets as sketches and 
make his drawings directly from them, working to the 
given dimensions. 

Each detail on this sheet should be carefully studied 
and the reason for each line and dimension should, 
with the aid of the preceding explanations, be under- 
stood. 



SHEET XXVI 






*Sp/nd/e -^ 



T' 


1 - 


It 


t 


ill- 


-t-- 




Bench LothQ. 
Details oF Head Stock. 

3-4-96. AC 

L-2-2 



74 



COURSE IN MECHANICAL DRAWING. 



SHEET XXVII. 

Bench Lathe— Details of Tool Rest. 



But two views of the post are necessary to give all 
the dimensions ; the bottom view shows a little more 
clearly the shape of that part of the post. The tap 
(internal screw-threading) on the post is shown by 
parallel hidden lines in the side view and by the 
note, "I in. tap." The tap is shown in the front view 



by two circles. This method is also shown on the 
clamping lever. Where a definite pitch is not given 
of screw threads, as in the case of the fastening bolt, 
it is understood to be standard. The bolt is five- 
eighths inches in diameter, therefore the pitch of the 
screw-threading is eleven. (See Table on page 38.) 



SHEET XXVII 



5ac/c//B --* 



f!est -/ 



■^-dy ^ Ff 1 > Ii>K^ 



.^^^ 



-Ji- 




/Anchor P/ofe-S- 



~^ 



C/ampjng Scref>^~*3. 
2y: ' 



k 2-- 




10 


__ . --^ 





t-^ 


^,?- .! 



■ I I I 



_ia 



T_y 



I 



fTif--i 



Bench Laths 
Detoifs of Tool Rest 

2~2Q~9G .?t^« oe-.. 

L-2-3 



76 



COURSE IN MECHANICAL DRAWING. 



SHEET XXVIIl. 



Bench Lathe — Details of Tail Stock. 



But one view of the nuts is shown, and in each 
case the height alone is given. This would indicate 
that the nuts are standard, and the height of the nut 
equals the diameter of the bolt. 1 herefore, the taps 
of the stud bolt nut and the hand wheel nut are 



■|-inches and |-inches respectively. Another method 
of indicating a tap is given on the tail stock frame, 
where the thread is shown by conventional hidden lines. 
The taper of the centre might have been expressed 
by giving the amount of rise to each inch. 



SHEET XXVIII 



, Stcd Bolt -13. 



Hond vyheel-G. 




k^fM= 



Bench Lathe 
Details oF Toil 5tock 

■ SCAL£ - r-Vt-L. StZ£ 

2-17-96 OK.eci. 



;8 



COURSE IN MECHANICAL DRA WING. 



SHEET XXIX. 

Bench Lathe — Details of Bed. 



This sheet is drawn to half-scale. As the structure 
of the bed is the same throughout a considerable 
length, space may be saved by breaking out a piece 
and showing only the ends. The dimension over- 
all is siven. The section here shown as an end view is 
frequently drawn in the broken-out portion as indicat- 



ing the structure of the object at that part. 



times drawings made to different scales are 



Some- 
placed 

upon the same sheet. On this sheet the bed and 
leg are drawn to half-scale, but the bolt might 
have been drawn full size, on account of its relative 
smallness, and a note giving its scale added. 



SHEET XXIX 



Bed-/ 




Bench Lathe. 
Deta'ila of Bed 

s-zo-se Oif c 

L-2-5 



PARALLEL COURSE. 



M 



PARALLEL COURSE EXERCISES 



The following exercises constitute an independent 
series, parallel to the regular course, and may be pur- 
sued in preference to the regular course by those who 
desire to avoid any tendency towards copying. Each 
sheet differs but slightly from the corresponding sheet 
of the regular course, and may readily be drawn from 
the directions accompanying the regular sheet. 



EXERCISE I. 
Square Prisms. Draw the top and front views of 
a square prism, the base of which is 2 inches square 
and the height 3 inches. Show three positions as in 
Sheet I. 

EXERCISE II. 
Triangular and Hexagfonal Pyramids, A pyramid 
differs from a prism in that its sides meet in a point. 
Draw the top and front views of a triangular pyramid 
4 inches in height and having each side of the base 
2 inches. Also draw the top, front, and left-hand 
views of a hexagonal pyramid 4 inches in height, 
having each side of the base li inches. 



EXERCISE III. 
Projection of a Square Prism. Draw the front, 
top and two side views of a square prism, having an 
altitude of 4 inches, base 2 inches square, and tilted 
30° to the right. 

EXERCISE IV. 
Projection of a Double Cross. Add to the cross 
shown in Sheet IV another arm, at right angles to 
the one given, and of similar dimensions. The top 
view will then present a cross, the arms of which are 
each one inch square. Draw the various projections 
shown in Sheet IV. 

EXERCISE V. 

Sectioned Views. Draw the top and front views, 
and half-section of a square prism, 4 inches high, 
with 2l-inch base, and having a bore of li inches in 
diameter. 

Also draw the top and front views of a similar 
prism having a flange at the top and bottom l inch 
high and overhanging i inch. Show one-half of the 
front view in section. 



84 



COURSE IN MECHANICAL DRAWING. 



EXERCISES VI AND VII. 
Joints. Make working drawings of two simple 
joints, as of a Lap Joint and a Sash Joint. 

EXERCISE VIII. 
Development of a Rectangular Block. Draw 
the development of the surface of a rectangular block, 
3 inches long, 2 inches deep, and 2^ inches high. 

EXERCISE IX. 
Development of a Rectangular Pyramid. Draw 
the top and front views, and the development of the 
entire surface of a pyramid having a rectangular base 
2^ X 2 inches, and an altitude of 4 inches. 

EXERCISE X. 
Development of a Truncated Square Pyramid. 

At half the altitude of the square pyramid of Sheet 
IX make a cut at 45° to the base and develop the 
entire surface of the lower part, including the cut 
surface. It will be necessary to show the cut in the 
top view, and this may be obtained by projecting the 
intersections of the cut and the sides of the pyramid 
to these sides as shown in the top view, and by 
joining the points thus found. The entire drawing of 
Sheet IX should first be made, as the cut is then 
more readily determined. 



EXERCISE XI. 
Development of an Elliptical Cylinder. Draw 
the top and front, views, and the development of a 
cylinder having an altitude of 4 inches, and an ellip- 
tical base, the major (longer) axis of the ellipse being 
2I inches and the minor (shorter) axis 1 1 inches. Cut 
the cyhnder by an inclined plane and' develop the cut. 
The ellipse is stepped off into a number of equal 
parts as in the case of the circle in Sheet XI. 

C 




D 

Fig. 4. 

A simple method of drawing a true ellipse, when 
the major and minor axes are known, is shown in the 
diagram Fig. 4. Let A B be the major axis and C D the 
minor axis. On a slip of paper lay off E F equal to 



PARALLEL COURSE EXERCISES. 



85 



one-half A B, and G F equal to one-half C D. Then 
keeping the point E always on the line C D and the 
point G always on the line A B, the point F will 
describe the required ellipse. Find a number of 
positions of the point F and through these points 
draw a smooth curve. 

EXERCISE XII. 
Development of an Elliptical Cone. Draw the 
top and front views, and the development of a cone 
having an altitude of 4 inches, and an elliptical base, 
the major axis of the ellipse being z\ inches and the 
minor a.xis 1 1 inches. Cut the cone by an inclined 
plane and develop the cut. 



EXERCISE XIII. 

Development of a Five=Piece Elbow. Draw 
the front view and development of a five-piece elbow 
of the same general dimensions as given for the four- 
piece elbow. 



should, therefore, not be attempted. A slight varia- 
tion of the dimension given is the only change that 
should be made. This will 
somewhat different curvature to the lines, 



be sufficient to give a 



EXERCISE XV. 

Springs. Sheet XV may be varied by closing the 
springs until the spaces are but three-quarters of the 
distances given, while the other dimensions remain 
the same. 



EXERCISE XVI. 
Bolts and Nuts. Substitute for the two bolts and 
nuts of Sheet XVI similar ones of 



I inches diameter 



of bolt, and 7 inches in length. Lay lengthwise of 
the sheet and draw without the top views of the nuts, 
by the method given in the latter part of the 
explanations accompanying Sheet XVI. Give all 
dimensions shown by letters in Sheet XVI. 



EXERCISE XIV. 

Screw Threads. The regular sheet on Screw 
Threads contains, in a compact form, much with 
which the student of the subject should be familiar. 
Any departure from the general make-up of the sheet 



EXERCISES XVII TO XXIV. 
Simple Working Drawings. Make working 
drawings of small articles that are not complex in 
their character. The following list may be suggestive 
of suitable material : 



86 



PARALLEL COURSE EXERCLSES. 



Various kinds of pulleys, clamps, wrenches, valves, 
simple vises, faucets, anvils; shafting details — as 
couplings, pillow-blocks, and hangers ; engine details 
— as ends, cranks, eccentrics, cross-heads and 
guides, etc. 



EXERCISES XXV TO XXIX. 

Working Drawings. Make a complete set of 
working drawings of some small machine, like a drill- 
press or bench-lathe, or of a small engine. 



